As a new type solid light source, the LED device not only has the advantages such as low power consumption, small volume, fast response speed, long working life, easy light regulation and color adjustment, energy saving and environmental protection, but also is highly superior to conventional light sources such as the incandescent lamp and the fluorescent lamp in the aspects of production, manufacturing and applicability. Thus the LED device has been significantly developed from its occurrence in 1960s. Currently, the LED device has been widely applied to various lighting fields, such as street lighting, landscape lighting, large screen display, traffic lights and indoor lighting.
The popular LED device is mainly achieved by exciting the yellow luminescent powder using the blue light. The conventional process forms the LED device by coating the mixed yellow luminescent powder and silica gel onto a blue chip and curing the silica gel through a heating. However, as for the LED device formed in the conventional process, the luminescent powder is directly contacted with the chip and the ambient temperature of the luminescent powder rises quickly when the chip works, thus the luminescent powder is aged due to the heat generated by the luminescence of the chip, and the luminous efficiency thereof is decreased. In addition, the chromaticity coordinates of the luminescent powder will also offset due to the temperature rise of the working environment, and finally influence the luminous efficiency, the emitting color and the service life of the LED device.
In order to solve the problem that the luminescent powder is easy to be aged in the conventional LED device, people have tried to dispose the luminescent powder and the chip separately during the manufacturing of the LED device. In the LED device of the prior art, although the luminescent powder is separated from the chip to slow down the aging speed of the luminescent powder, the obtained LED device has a small angle of emergence due to the limitation of the emergent angle of the LED chip. In addition, the light intensity distribution is nonuniform, i.e., at the same height from the chip, the light intensity is the strongest near around the right front of the chip, and gradually decreased with the increase of the distance to the center.